The present invention relates to temperature self-regulating dual surface heaters and more particularly to a heater having opposed faces which may be self-regulated at the same or different temperatures for multi purposes including butt fusion of plastic pipe, shelf heater in vending machines and the like.
In butt fusion of plastic pipes, the ends of the pipes are individually heated to fusion temperature by cartridge heaters that heat up the entire housing and thus are quite inefficient. This problem becomes apparent when it is realized that the housing is large and made of aluminum and thus presents a substantial mass that must be heated. Also the device is quite heavy and difficult to use. Further the temperature distribution in such an arrangement is poor and long heat up and cool down times are encountered.
In the field of vending machines, food to be heated is taken from the machine and heated in a microwave or other oven. When the food, such as soup is in a metal can and a microwave oven used, the food must be removed from the metal container and placed in a non-metallic dish for heating. At lunch time lines often form at the microwave as individuals a-wait the opportunity to heat their food.